Question

a tribble with the genotype ssll is crossed with a tribble with the genotype ssll. how many different genotypes can be expressed in the offspring
1
2
3
4

Explanation:

Step1: Analyze S allele cross

Parent 1 (Ss) × Parent 2 (ss). Gametes: S, s (from Ss); s, s (from ss). Offspring genotypes: Ss, ss (2 types).

Step2: Analyze L allele cross

Parent 1 (LL) × Parent 2 (Ll). Gametes: L (from LL); L, l (from Ll). Offspring genotypes: LL, Ll (2 types).

Step3: Combine results

Use product rule: 2 (S - genotypes) × 2 (L - genotypes) = 4. Wait, no—wait, Ss×ss gives Ss, ss (2); LL×Ll gives LL, Ll (2). Now combine each S - genotype with each L - genotype:

• Ss with LL: SsLL
• Ss with Ll: SsLl
• ss with LL: ssLL
• ss with Ll: ssLl

Total 4 different genotypes? Wait, no, wait original parents: first parent SsLL, second ssLl. So Ss×ss: Ss, ss (2). LL×Ll: LL, Ll (2). So combinations: 2×2=4. But wait, let's list them:
From Ss (first parent's S allele) and ss (second):

• Ss (from Ss×ss) with LL (from LL×Ll): SsLL
• Ss with Ll: SsLl
• ss (from Ss×ss) with LL: ssLL
• ss with Ll: ssLl

Yes, 4 different genotypes. Wait but maybe I made a mistake? Wait first parent: SsLL (so L is homozygous), second: ssLl (L is heterozygous). So for L locus: LL × Ll. Gametes: L (LL) and L, l (Ll). So offspring L genotypes: LL (L from LL and L from Ll), Ll (L from LL and l from Ll). So 2 L genotypes. For S locus: Ss × ss. Gametes: S, s (Ss) and s, s (ss). Offspring S genotypes: Ss (S from Ss and s from ss), ss (s from Ss and s from ss). 2 S genotypes. Then combine: SsLL, SsLl, ssLL, ssLl. That's 4. So the answer should be 4? Wait but the options have 4. Wait maybe my initial thought was wrong. Wait let's re - check.

Wait, first parent: SsLL (genotype), second: ssLl. So for S: Ss × ss. Possible genotypes: Ss, ss (2). For L: LL × Ll. Possible genotypes: LL, Ll (2). Now, each S - genotype can pair with each L - genotype. So Ss with LL: SsLL; Ss with Ll: SsLl; ss with LL: ssLL; ss with Ll: ssLl. That's 4 distinct genotypes. So the number is 4.

Answer:

4 (the option with "4")